Opponents to the roundabout are growing in volume — both audibly and by head count — if a public hearing at the Martha’s Vineyard Commission last week was any indication.

The opponents crowded into the Olde Stone Building in Oak Bluffs on Thursday night, ready to launch one last salvo against the traffic improvement plan for the intersection of Barnes and Edgartown-Vineyard Haven Roads, as the commission wraps up a review of the project as a development of regional impact (DRI). The plan has the backing of the Oak Bluffs selectmen and state transportation officials.

At the outset on Thursday commissioner Doug Sederholm warned that the only reason he had continued the public hearing from Sept. 1 was to receive oral testimony from Vineyard Transit Authority administrator Angela Grant about the placement of six bus stops near the roundabout. But the group of some 30 staunch opponents were there to protest the safety and aesthetics and question the necessity of the $1.2 million project.

Sandra Lippins who lives at the Tilton Rentall corner of the intersection was incredulous following the technical discussion about bus stops.

“I seem to be in a room full of people where this is a done deal,” she said. “I can’t believe what I’m hearing.”

Island businessman Clarence A. (Trip) Barnes 3rd was more animated, claiming that his trucks would not be able to maneuver through the roundabout. Last Sunday he held a demonstration at the Steamship Authority bus turnaround in Vineyard Haven during which his trucks had difficulty making U-turns around the circle.

“It’s not going to work,” he said. “It’s absolutely ludicrous, you’re being fed a bunch of crap here.”

The diameter of the roundabout will be 105 feet; the diameter of the steamship turnaround is 96 feet.

“These are traffic engineers,” said commission senior planner Bill Veno. “Why wouldn’t they design something that can’t accommodate a truck?”

But Mr. Barnes wasn’t finished. In 2004 Madeline Fisher collected 1,400 signatures opposed to the roundabout. In a separate petition in 2006 she collected 1,800 signatures. Mr. Barnes invited her to present the signatures to the commission and helped her unfurl a banner of names that stretched some 10 feet across the room.

“Talk about being ignored,” said Mr. Barnes.

Craig Hockmeyer of Craig’s Bicycles in Vineyard Haven has long been concerned about the roundabout’s implications for those not driving through it.

“You said it yourself in your 2006 staff report that motorists failed to yield to pedestrians in crosswalks at a higher rate than at stop signs or signals,” he said. “How is a pedestrian or a cyclist going to get across? There has been no answer. Simply ignoring it and saying we like roundabouts because our statistics say it’s safer is not a good answer.”

Other attendees testified about their harrowing experiences on off-Island roundabouts.

“I’m concerned that a lot of people who want the roundabout have not been on one,” said Julianne Van Belle of West Tisbury. “It’s true that the roundabout at Marstons Mills is different than a rotary. I didn’t feel I needed the skills of a Nascar race driver to navigate through it, however I did feel oddly transported as though I were in a bumper car ride in an amusement park. It did not feel safe, it did not feel calming.”

Christine Miller offered her perspective as a bicyclist on Nantucket’s roundabout.

“The traffic is always moving so you’re running from your bike from one island to the other and you absolutely never feel safe,” she said. “This roundabout is all about motor vehicles.”

The state was set to advertise for the project this fall but on Thursday the commission was reluctant to speed up their process to accommodate that schedule.

“Why are we treating the state differently than any other applicant?” asked commissioner Leonard Jason Jr.

Mr. Sederholm closed the public hearing but kept the written record open until noon on Oct. 3 to allow the Massachusetts Department of Transportation to respond to a number of unanswered questions about the project, including the total area of new hard surface created by the roundabout and its safety for pedestrians and bicyclists. The commission land use planning committee will meet at 5:30 p.m. on Monday to discuss the project. The full commission is expected to vote on the roundabout next Thursday.